I've looked for a mod that could do this using various search terms in the plugin management install area, on the site, and by using Google. I haven't found anything that is able to do this but it is something I consider would make using ST3 more efficient.
Does such a mod exist, or would one need to be created? Ideally, being able to split panels in half, and being able to dock panels by default would be a welcome addition. Docking options would include: Left, Right, Top, Top-Extended ( L and / or R ), Bottom, Bottom-Extended ( L/ and / or R )... Extended option would cause that panel to extend all the way to the program border with the option to only extend on the left or right sides, or both.